Powder molding apparatus and compact manufacturing method

ABSTRACT

Provided is a powder molding apparatus including: a die; an upper punch and a lower punch; a middle platen attached to the upper punch; an upper platen mounted on a press machine and the upper platen being attached to a push rod; a link mechanism connecting the upper platen and the middle platen; a first actuator that fixes the link mechanism and cancels a fixation of the link mechanism; a bolster attached to the lower punch, and a lower platen attached to the die, in which descending of the upper platen and the push rod causes the lower platen and the die to be pushed downward by the push rod, and along with a downward movement of the die, the lower punch makes a upward movement inside the hollow with respect to the die.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2015-185134 filed onSep. 18, 2015 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a powder molding apparatus and acompact manufacturing method using the apparatus.

2. Description of Related Art

various types of sintered parts are manufactured by press-molding metalpowder into a compact and sintering the compact.

In the aforementioned press molding, using a powder molding apparatusincluding a die having a hollow and an upper punch and a lower punchthat slide inside the hollow of the die and form a cavity jointly withthe hollow, a metal powder body is charged into the cavity and ispressurized by pushing down, for example, the upper punch, whereby apowder compact is manufactured.

Japanese Patent Application Publication No. 6-188138 discloses a moldingapparatus in which when a compact is ejected from a die, the die ispulled down using an actuator provided below the die, and moldingapparatuses of this type are in common use.

Employment of the molding apparatus disclosed in JP 6-188138 A requiresproviding an actuator and a mechanism (e.g., a rod) that connects theactuator and the die below the die, causing a problem in that a positionof the die from the ground is often high.

Also, for the convenience of work, the height of the die needs to be aheight that allows an upper surface of the die to be viewed by a worker,and thus, a problem also arises in that it is necessary to dig a pit ata site where a press is to be installed to embed a lower portion of thepress under the ground or it is necessary for the worker to stand on aplatform and perform work.

Furthermore, in ejection of a compact from the die, in order to preventcracking of the compact, it is necessary to apply a hold-down load (thecompact is ejected from the die in a state in which the compact is heldbetween the lower punch and the upper punch and a load for the holdingthe compact in this situation is referred to as “hold-down load”).

In order to keep the hold-down load constant, it is necessary to providea load cell to perform control; however, the load cell needs towithstand not only the hold-down load, but also a molding load,resulting in problems in that the molding apparatus itself tends tolarge in size and is often expensive.

SUMMARY OF THE INVENTION

The present invention provides a powder molding apparatus that enables amanufactured compact to be ejected easily without the need to make aheight of the molding apparatus to be high and the need to dig a pit ata site where a press is to be installed and, and a compact manufacturingmethod using the apparatus.

A powder molding apparatus according to an aspect of the presentinvention includes: a die having a hollow; an upper punch and a lowerpunch that slide inside the hollow of the die and form a cavity jointlywith an inner wall of the hollow; a middle platen attached to the upperpunch; an upper platen attached to a push rod; a press machine thatpushes down the upper platen; a link mechanism that connects the upperplaten and the middle platen; a first actuator that fixes the linkmechanism and cancels the fixation of the link mechanism; a bolsterattached to the lower punch; and a lower platen attached to the die, thelower platen being biased upward from the bolster via a spring, anddescending of the upper platen and the push rod causes the lower platenand the die to be pushed downward by the push rod, and along with adownward movement of the die, the lower punch makes a upward movementinside the hollow with respect to the die.

The powder molding apparatus according to the aspect of the presentinvention employs the configuration in which the first actuator fixes,and cancels the fixation of, a link mechanism connecting the upperplaten attached to the push rod (injection push rod), the push rodpushing down the lower platen equipped with the die, and the middleplaten equipped with the upper punch that slides inside the die.

At the time of molding for press-molding powder charged in the cavity,the link mechanism is fixed by the first actuator, a pressing force fromthe press machine is transmitted to the upper platen, the pressing forceis transmitted to the middle platen via the fixed link mechanism, andthe pressing force is then transmitted to the upper punch provided onthe middle platen, whereby the powder is press-molded.

On the other hand, when a molded compact is ejected from the cavity, thefirst actuator cancels the fixation of the link mechanism, and thepressing force from the press machine is transmitted to the upperplaten, but the pressing force is not transmitted to the middle platenvia the unfixed link mechanism.

Instead, the pressing force transmitted to the upper platen istransmitted to the lower platen equipped with the die by the push rod,whereby the lower platen and the die are pushed down. As a result of thedie being pushed down, the compact molded on the lower punch inside thehollow of the die is exposed above the die, enabling ejection of thecompact.

Examples of the first actuator can include, e.g., an air cylindermechanism and an oil hydraulic cylinder mechanism.

Also, examples of the press machine can include a slide and a unit bodyincluding an oil hydraulic cylinder or the like and a slide.

According to the powder molding apparatus according to the aspect of thepresent invention, in molding of powder and ejection of a compact,fixation and cancellation of the fixation of a link mechanism areperformed, respectively, by the first actuator, enabling themanufactured compact to be easily ejected without the need to make aheight of the molding apparatus to be high and the need to dig a pit ata site where the press is installed.

In the powder molding apparatus according to the aspect of the presentinvention, the link mechanism may include two links and three joints,the three joints connecting the links, the upper platen and the middleplaten, respectively, and connecting the two links.

In the powder molding apparatus according to the aspect of the presentinvention, the first actuator may include an air cylinder and a piston,and a distal end of the piston may be attached to the joint that is amiddle joint among the three joints.

Also, the powder molding apparatus according to the aspect of thepresent invention may further include a second actuator between theupper platen and the middle platen.

As with the first actuator, the second actuator includes, e.g., an aircylinder mechanism or an oil hydraulic cylinder mechanism.

After a compact is molded in the cavity, the fixation of the linkmechanism is cancelled by the first actuator, and a pressing force fromthe press machine is thus transmitted to the lower platen equipped withthe die, via the push rod to push the lower platen and the die down.Here, if the second actuator is not provided, no pressing force isapplied to the upper punch, but because of the provision of the secondactuator, the die can be pushed down while the compact being pressed bythe second actuator with a pressing force that is smaller than apressing force applied at the time of the molding.

In the second actuator, for example, a relief valve is provided,enabling a compact to be pressed while a load applied on the upper punch(what is called “hold-down load”) being kept constant by the secondactuator, and also a pressing force from the press machine to betransmitted to the lower platen equipped with the die, by the push rodto push the lower platen and the die down, whereby the compact isexposed from the cavity.

Also, the aspect of the present invention also provides a compactmanufacturing method, and the manufacturing method is a compactmanufacturing method using the above powder molding apparatus, themethod including: charging powder into the cavity; manufacturing acompact by fixing the link mechanism via the first actuator, and pushingdown the upper platen, the middle platen and the upper punch via thepress machine to mold the powder in the cavity; cancelling the fixationof the link mechanism via the first actuator, pushing down the upperplaten via the press machine, and pushing down the lower platen and thedie via the push rod to expose the compact from the cavity.

The manufacturing method according to the aspect of the presentinvention employs the powder molding apparatus according to the aspectof the present invention, enabling manufacture of a compact and ejectionof the manufactured compact from the cavity to be performed easily.

Also, during exposure of the compact from the cavity, a first pressingforce (hold-down load) is applied from the second actuator to the upperpunch to expose the compact from the cavity while the compact beingpressed by the first pressing force, the first pressing force beinglower than a second pressing force applied to push down the upperplaten, the middle platen and the upper punch via the press machine tomold the powder in the cavity.

As can be understood from the above statement, with the powder moldingapparatus according to the aspect of the present invention and thecompact manufacturing method according to the aspect of the presentinvention, in molding of powder and ejection of a compact, fixation andcancellation of the fixation of the link mechanism are performed,respectively, by the first actuator, enabling the manufactured compactto be easily ejected without the need to make a height of the moldingapparatus to be high and the need to dig a pit at a site where the pressis installed.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the invention will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a schematic diagram of Embodiment 1 of a powder moldingapparatus according to an aspect of the present invention;

FIG. 2 is a schematic diagram illustrating a state in which a compact isbeing manufactured in Embodiment 1 of the powder molding apparatus;

FIG. 3 is a schematic diagram illustrating a state in which a compact isexposed from a cavity so that the compact can be ejected in Embodiment 1of the powder molding apparatus;

FIG. 4 is a schematic diagram of Embodiment 2 of the powder moldingapparatus;

FIG. 5 is a schematic diagram illustrating a state in which a compact isbeing manufactured in Embodiment 2 of the powder molding apparatus;

FIG. 6 is a schematic diagram illustrating a state in which a compact isexposed from a cavity in Embodiment 2 of the powder molding apparatus;and

FIG. 7 is a schematic diagram illustrating a state in which the compactis exposed from the cavity so that the compact can be ejected inEmbodiment 2 of the powder molding apparatus.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments 1 and 2 of a powder molding apparatus according to thepresent invention and compact manufacturing methods will be describedbelow with reference to the drawings.

(Embodiment 1 of powder molding apparatus and compact manufacturingmethod) FIG. 1 is a schematic diagram of Embodiment 1 of a powdermolding apparatus according to the present invention, FIG. 2 is aschematic diagram illustrating a state in which a compact is beingmanufactured in Embodiment 1 of the powder molding apparatus, and FIG. 3is a schematic diagram illustrating a state in which the compact isexposed from a cavity so that the compact can be ejected in Embodiment 1of the powder molding apparatus.

The illustrated powder molding apparatus 200 roughly includes a pressmachine 70 installed in a frame 100, a die 10, an upper punch 20 and alower punch 30, a middle platen 50 with the upper punch 20 attachedthereto, an upper platen 40, a link mechanism 90 connecting the upperplaten 40 and the middle platen 50, a first actuator 80 that fixes andcancels the fixation of the link mechanism 90, a bolster 61 with thelower punch 30 attached thereto, and a lower platen 60 with the die 10attached thereto.

The lower punch 30 and the upper punch 20 are slidable inside a hollow11 of the die 10, and in FIG. 1, metal powder F to be press-molded ischarged in a cavity defined by the hollow 11 and the lower punch 30.

The upper punch 20 is attached to a lower surface of the middle platen50 via a retainer 53, and first guide posts 54 are attached to an uppersurface of the middle platen 50.

Also, a stopper 51 that holds a fixed position of the link mechanism 90and a first actuator attachment portion 52 are provided on the uppersurface of the middle platen 50.

First guide bushes 40 a through which the respective first guide posts54 extend are provided in the upper platen 40, a slider 72 included inthe press machine 70 is mounted on an upper surface of the upper platen40, and push rods 41 are attached to a lower surface of the upper platen40.

The lower punch 30 is attached to an upper surface of the bolster 61 viaa retainer 63, and second guide posts 62 are also attached to the uppersurface of the bolster 61.

Second guide bushes 60 a through which the second guide posts 62 extendare provided in the lower platen 60, and the die 10 is attached at thecenter of the lower platen 60.

A spring 64 is disposed around a periphery of each second guide post 62projecting from the upper surface of the bolster 61, and the springs 64support the lower platen 60 while biasing the lower platen 60 upward.

The press machine 70 includes an oil hydraulic cylinder 71 that slides apiston 71 a, and a slider 72 that receives a pressing force from thepiston 71 a.

The components of the powder molding apparatus 200 are housed in theframe 100, and the oil hydraulic cylinder 71 included in the pressmachine 70 is fixed on a top surface of the frame, and the piston 71 aextends through the top surface and projects to the inside of the frame100, and a distal end of the piston 71 a is fixed to the slider 72.

The link mechanism 90 includes two links 91 and three joints 92, thethree joints 92 connecting the links 91 to the upper platen 40 and themiddle platen 50, respectively, and connecting the two links 91 to eachother.

The first actuator 80 includes an air cylinder 81 and a piston 82, and adistal end of the piston 82 is attached to the joint 92 that is a middlejoint among the three joints 92.

FIG. 1 illustrates a state in which the piston 82 has moved to a leftend of the air cylinder 81 (Z1 direction) and fixes the two links 91, 91linearly.

As illustrated in FIG. 1, metal powder F is charged in the cavity, andthe link mechanism 90 is fixed linearly by the first actuator 80, andthen, as illustrated in FIG. 2, the press machine 70 is activated toslide the piston 71 a to provide a pressing force P to the upper platen40 via the slider 72.

Upon receipt of the pressing force P, the upper platen 40 pushes downthe middle platen 50 and the upper punch 20 fixed to the lower surfaceof the middle platen 50 (X1 direction) via the link mechanism 90 fixedlinearly by the first actuator 80, and the metal powder F is molded inthe cavity defined by the die 10 and the lower punch 30, whereby acompact C is manufactured.

After the manufacture of the compact C, next, the compact C is ejectedfrom the cavity.

More specifically, as illustrated in FIG. 3, the piston 82 movesrightward inside the air cylinder 81 of the first actuator 80 (Z2direction) to pivot the two links 91, 91 included in the link mechanism90 around the respective joints 92 (respective Y1 directions), wherebythe linear fixation of the link mechanism 90 is cancelled.

Upon the press machine 70 being activated (pressing force P′)concurrently with the cancellation of the fixation of the link mechanism90, the lower platen 60 and the die 10 are pushed down against thebiasing force from the spring 64, via the push rods 41 (X2 direction)while the pressing of the compact C by the upper punch 20 beingcancelled.

As a result of the die 10 being pushed down, the compact C in the cavitymoves upward relative to the die 10 (X3 direction) and the compact C isthen exposed to the outside of the cavity and the compact C can thus beejected.

As described above, according to the powder molding apparatus 200, inmolding of metal powder F and ejection of a compact C, fixation andcancellation of the fixation of the link mechanism 90 are performed,respectively, by the first actuator 80, enabling a manufactured compactto be easily ejected without the need to make a height of the powdermolding apparatus 200 to be high and the need to dig a pit at a sitewhere the press is installed.

(Embodiment 2 of powder molding apparatus and compact manufacturingmethod) FIG. 4 is a schematic diagram of Embodiment 2 of the powdermolding apparatus, and FIG. 5 is a schematic diagram illustrating astate in which a compact is being manufactured in Embodiment 2 of thepowder molding apparatus. Also, FIG. 6 is a schematic diagramillustrating a state in which the compact is exposed from a cavity inEmbodiment 2 of the powder molding apparatus, and FIG. 7 is a schematicdiagram illustrating a state in which the compact is exposed from thecavity so that the compact can be ejected in Embodiment 2 of the powdermolding apparatus.

A powder molding apparatus 200A, which is illustrated in FIG. 4, is anapparatus obtained by adding two second actuators 80A connecting theupper platen 40 and the middle platen 50 to the powder molding apparatus200.

As illustrated in FIG. 4, the two second actuators 80A each include anair cylinder 81A and a piston 82A, and is disposed in such a manner thatthe piston 82A moves up/down vertically.

In each of the second actuators 80A, a non-illustrated relief valve isprovided, whereby a compact C is pressed while a load applied on anupper punch 20 (what is called “hold-down load”) being kept constant bythe second actuators 80A (see FIG. 6), and a pressing force from a pressmachine 70 is transmitted to a lower platen 60 equipped with a die 10 bypush rods 41, thereby the compact C being exposed to the outside of thecavity.

In other words, the second actuators 80A are actuators for applying aconstant hold-down load to a compact C when the compact C is ejected.

Here, a compact manufacturing method using the powder molding apparatus200A will generally be described.

As illustrated in FIG. 5, the press machine 70 is activated to apply apressing force P to a middle platen 50 and the upper punch 20 fixed to alower surface of the middle platen 50 via a link mechanism 90 fixedlinearly by the first actuator 80 to push down the middle platen 50 andthe upper punch 20 (X1 direction), whereby a compact C is manufacturedin the cavity defined by the die 10 and a lower punch 30.

Next, as illustrated in FIG. 6, a piston 82 is moved rightward (Z2direction) inside an air cylinder 81 of the first actuator 80 to pivottwo links 91, 91 included in the link mechanism 90 around respectivejoints 92 (respective Y1 directions), whereby the linear fixation of thelink mechanism 90 is cancelled.

Furthermore, the pistons 82A are moved upward inside the air cylinders81A of the respective second actuators 80A (Z3 direction) to apply aconstant hold-down load from the second actuators 80A to the middleplaten 50 (X4 direction) and apply the constant hold-down load to theupper punch 20 via the middle platen 50 (X5 direction).

With the compact C held by the constant hold-down load, a pressing forceV from the press machine 70 pushes down the lower platen 60 and the die10 against a biasing force of the spring 64, via the push rods 41 (X2direction).

As illustrated in FIG. 6, as a result of the die 10 being pushed down,the compact C in the cavity moves upward relative to the die 10 (X3direction).

As illustrated in FIG. 7, the pistons 82A are moved further upwardinside the air cylinders 81A of the respective second actuators 80A (Z4direction) to move the middle platen 50 and the upper punch 20 upward(X6 direction), whereby the compact C exposed to the outside of thecavity can be ejected.

In addition to the effects provided when the powder molding apparatus200 is used, the powder molding apparatus 200A can prevent a compact Cfrom cracking when the compact C is ejected from the die 10.

Although the embodiments of the present invention have been described indetail with reference to the drawings, the specific configurations arenot limited to those of these embodiments, and alternations in designand the like of such specific configurations without departing from thespirit of the present invention also fall within the scope of thepresent invention.

What is claimed is:
 1. A powder molding apparatus comprising: a diehaving a hollow; an upper punch and a lower punch that slide inside thehollow of the die and form a cavity jointly with an inner wall of thehollow; a middle platen attached to the upper punch; an upper platenattached to a push rod; a press machine that pushes down the upperplaten; a link mechanism that connects the upper platen and the middleplaten; a first actuator that fixes the link mechanism and cancels afixation of the link mechanism; a bolster attached to the lower punch;and a lower platen attached to the die, the lower platen being biasedupward from the bolster via a spring, wherein descending of the upperplaten and the push rod causes the lower platen and the die to be pusheddownward by the push rod, and along with a downward movement of the die,the lower punch makes a upward movement inside the hollow with respectto the die.
 2. The powder molding apparatus according to claim 1,wherein the link mechanism includes two links and three joints, thethree joints connecting the links, the upper platen and the middleplaten, respectively, and connecting the two links.
 3. The powdermolding apparatus according to claim 2, wherein the first actuatorincludes an air cylinder and a piston, and a distal end of the piston isattached to the joint that is a middle joint among the three joints. 4.The powder molding apparatus according to claim 1, further comprising asecond actuator between the upper platen and the middle platen.
 5. Thepowder molding apparatus according to claim 4, wherein a relief valve isprovided in the second actuator.
 6. A compact manufacturing method usingthe powder molding apparatus according to claim 1, the methodcomprising: charging powder into the cavity; manufacturing a compact byfixing the link mechanism via the first actuator, and pushing down theupper platen, the middle platen and the upper punch via the pressmachine to mold the powder in the cavity; cancelling the fixation of thelink mechanism via the first actuator, pushing down the upper platen viathe press machine, and pushing down the lower platen and the die via thepush rod to expose the compact from the cavity.
 7. The compactmanufacturing method according to claim 6, wherein the powder moldingapparatus according to claim 4 is used, during exposure of the compactfrom the cavity, a first pressing force is applied from the secondactuator to the upper punch to expose the compact from the cavity whilethe compact being pressed by the first pressing force, the firstpressing force being lower than a second pressing force applied to pushdown the upper platen, the middle platen and the upper punch via thepress machine to mold the powder in the cavity.